diff --git a/common.mk b/common.mk
index 75419e30..29c2713b 100644
--- a/common.mk
+++ b/common.mk
@@ -70,8 +70,6 @@ $(HARNESS_SMEMS_FILE) $(HARNESS_SMEMS_FIR): $(HARNESS_SMEMS_CONF)
 ########################################################################################
 # remove duplicate/*.h files in blackbox/simfiles
 ########################################################################################
-sim_files ?= $(build_dir)/sim_files.common.f
-
 $(sim_files): $(sim_top_blackboxes) $(sim_harness_blackboxes) $(sim_dotf)
 	awk '{print $1;}' $^ | sort -u | grep -v ".*\.h" > $@
 
diff --git a/variables.mk b/variables.mk
index 7aefdd18..06e08136 100644
--- a/variables.mk
+++ b/variables.mk
@@ -122,6 +122,7 @@ HARNESS_SMEMS_FIR  ?= $(build_dir)/$(long_name).harness.mems.fir
 SMEMS_FILE         ?= $(build_dir)/$(long_name).mems.v
 SMEMS_CONF         ?= $(build_dir)/$(long_name).mems.conf
 SMEMS_FIR          ?= $(build_dir)/$(long_name).mems.fir
+sim_files              ?= $(build_dir)/sim_files.common.f
 sim_dotf               ?= $(build_dir)/sim_files.f
 sim_harness_blackboxes ?= $(build_dir)/firrtl_black_box_resource_files.harness.f
 sim_top_blackboxes     ?= $(build_dir)/firrtl_black_box_resource_files.top.f